It's a great graphic, but I'll nitpick. There's an important distinction that's left out. During all the stages leading to the Ph.D., all the area covered was just learning, taking in what other people have done. The very last little bump on the other hand actually added new area, so it's a very different thing, you're discovering new knowledge as opposed to just learning about what's already known. I suppose the graphic does capture that in a way but it's subtle.